. A PRELIMINARY TECHNICAL RESULT

A technical Lemma is needed, which forms the basis of the Main Loop Theorem (see subsection 4.4 of chapter 1). Let P a complex matrix and Ді and Д2 two mixed model perturbations. The two interconnection structures of Figure 12.4 are equivalent, if Д = diag( Ді, Д2). Partition then compatibly P as: